On Sunday, Dec. 16, the comet known as 46P/Wirtanen will make one of the 10 closest comet flybys of Earth in 70 years, and you may even be able to see it without a telescope!
Although the approach will be a distant 7.1 million miles from Earth, it's still a fairly rare opportunity. This is the closet the comet will come to Earth for centuries! It will also be one of the brightest comets in years. This will offer astronomers an important opportunity to study a comet up close with ground-based telescopes, both optical and radar. Comet Wirtanen has already been visible in larger amateur telescopes, and while the brightness of comets is notoriously difficult to predict, there is the possibility that during its close approach comet Wirtanen could be visible with binoculars or to the naked eye!
The comet will appear the brightest today, and since it was too cloudy to catch earlier this morning, tonight would be a good time to try! It is still cloudy right now (mid morning), but clouds are going to try and erode through the day. By tonight, it looks like we will have fewer clouds around than this morning/last night, making it easier to find the comet.
The comet was discovered by Astronomer Carl Wirtanen 1948 in California. It orbits the Sun fairly quickly for a comet — once every 5.4 years — making it a short-period comet. Some comets have orbital periods greater than 200 years! At the time of closest approach, the comet will appear to be located in the constellation Taurus close to the Pleiades and above Orion's Belt. Be sure to avoid light pollution. Even though it is brightest on the 16th, it is still visible for a week or two later. The moon is also something to consider. The moon becomes full on the 22nd, but on Christmas Eve, there will about an hour of darkness between twilight and the moonrise. On NYE, the comet will also be higher in the sky (70 degrees above the horizon) making it easier to see.
To learn more, the Comet Wirtanen Observing Campaign website is: http://wirtanen.astro.umd.edu
